The World Economic Forum at Davos, Switzerland sounds  like a pretty crazy place to be right now. Paloma Faith is there. So is Prince Andrew. And Will.i.am showed up at a Wall Street Journal party.

But crazier than all this – crazier, even, than Pharell Williams saying at the conference today that he is “literally going to have humanity harmonise all at once” – is a proposal from ex-president of Mexico Felipe Calderon and former US vice-president Al Gore to, essentially, ban cars from every city in the world.  

As part of a presentation from the Global Commission on the Economy & Climate (GCEC), Calderon and Gore argued that the fight against global warming will necessitate new, car-free city designs: urban areas, after all, are responsible for around 70 per cent of greenhouse gas emissions. Calderon told the conference:

We cannot have these cities with low density, designed for the use of cars… We recommend those cities should have more density and more mass transportation.

Designing cars out of every city and future city would apparently require a mere $90trn in infrastructure investment. 

This isn’t actually as outlandish as it sounds: after the talk, Calderon told Business Insider that $90trn will be spend in coming years building and upgrading cities worldwide anyway. The GCEC’s argument is that the money should be spent on infrastructure unfriendly to cars, and on creating denser communities – essentially, undoing all the damage of the car-based city designs we’ve used for centries.

A GCEC report on city carbon emissions compares the footprint and carbon emissions in two cities with similar-sized populations to demonstrate their point about density. On the left is Atlanta; on the right is Barcelona. Spot the difference.

Click for a larger image.

Barcelona covers 1/26th of the area of Atlanta, has a slightly higher population – yet it produces just over a tenth of the transport carbon emissions.

So, the GCEC clearly has a point – but what’s less clear is how you’d decrease the footprint of already-sprawling cities, even if you do have $90trn in your pocket.